This disclosure relates generally to feeding cut sheet media through an electrophotographic printing machine. More particularly, the present disclosure relates to transport devices for directing the flow of cut sheet media within an electrophotographic printing machine.
In a typical electrophotographic printing process, a photoconductive member is charged to a substantially uniform potential so as to sensitize the surface thereof. The charged portion of the photoconductive member is exposed to a light image of an original document being reproduced. Exposure of the charged photoconductive member selectively dissipates the charges thereon in the irradiated areas. This records an electrostatic latent image on the photoconductive member corresponding to the informational areas contained within the original document. After the electrostatic latent image is recorded on the photoconductive member, the latent image is developed by bringing a developer material into contact therewith. Generally, the developer material comprises toner particles adhering triboelectrically to carrier granules. The toner particles are attracted from the carrier granules to the latent image forming a toner powder image on the photoconductive member. The toner powder image is then transferred from the photoconductive member to a copy sheet. The toner particles are heated to permanently affix the powder image to the copy sheet.
High speed copying machines are becoming increasingly popular. These machines have a capacity or output capacity of say, for example, over 60 copies per minute. These machines are able to use single cut sheets of paper of various size such as A4, 8½×11, or 8½×14 inch copy sheets. These machines may be of the light lens, xerographic machine or may be a printer with digital input. Single, cut sheet printing machines are now available at speeds around 200 cpm.
As xerographic and other copiers increase in speed, and become more automatic, it is increasingly important to provide higher speed yet more economical, reliable and more automatic handling of both the copy sheets being made by the copier and the original document sheets being copied. It is thus desired to accommodate sheets which may vary widely in size, weight, thickness, material, condition, humidity, age, etc. These variations change the beam strength or flexural resistance, as well as, other characteristics of the sheets. Yet, the desire for automatic and high speed handling of such sheets without jams, misfeeds, uneven feeding times, or other interruptions increases the need for reliability of all sheet handling components.
Sheet inverters are one such sheet handling component with particular reliability problems and sheet handling size and capability limitations. Although a sheet inverter is referred to in the copier art as an inverter, its function is not necessary to immediately turn the sheet over (i.e., exchange one face for the other). Its function is to effectively reverse the sheet orientation in its direction of motion. That is, to reverse the lead edge and trail edge orientation of the sheet.
Typically, in an inverting device, the sheet is driven or fed by feed rollers or other suitable sheet driving mechanisms into a sheet reversing chute. By then, reversing the motion of the sheet within the chute and feeding it back out from the chute, the desired reversal of the leading and trailing edges of the sheet in the sheet path is accomplished.
Depending on the location and orientation of the inverter in a particular sheet path, this may, or may not, also accomplish the inversion (turning over) of the sheet. In some applications for example, where the (inverter) is located at a corner of a 90° to 180° inherent bend in the copier sheet path, the inverter may be used to actually prevent inverting of a sheet at that point, i.e., to maintain the same side of the sheet face-up before and after this bend in the sheet path. On the other hand, if the entry and departing path of the sheet, to and from the inverter, is in substantially the same plane, the sheet will be inverted by the inverter. While inverters have numerous applications in the handling of either original documents or copy sheets, their role is still limited to either maintaining, or reversing the sheet orientation.